The present invention relates to improvements in the structure and method of assembly or fabrication of keypads, and more particularly to those types of multi-character devices electrically responsive to manual pressure applied to selected areas of a flexible sheet covering individual actuating members.
Keypads are used in many applications, normally in conjunction with other electrically operated devices or systems to provide inputs controlling operational parameters thereof. A number of basic types or structures of keypads are currently in widespread use. Some types, for example, are actuable by manual deformation of a layer of conductive rubber, or a metal spring member into contact with conductive portions of printed circuit boards.
Another popular type of keypad is actuated by manual pressure applied to selected areas of a continuous, flexible sheet, e.g., of Mylar or other suitable plastic, to which conductive ink has been applied by silk screening, or other such process. Such keypads are generally referred to as being of the membrane type and sometimes incorporate dome-type spring members to provide a more discernable feel or tactile response to a user when manual pressure is applied. Although membrane-type keypads may be fabricated at low cost by present-day manufacturing techniques, the cost of repairing or replacing individual defective components is so high in relation to the initial cost of the entire keypad that it is usual practise to discard a keypad upon malfunction of any portion thereof.
It is a principal object of the present invention to provide a keypad which has the look and feel of a conventional membrane-type device, but may be repaired at a cost far less than the replacement cost of the keypad.
Another object is to provide an economically repairable keypad having desirable tactile response characteristics.
A more general object is to provide improved keypad constructions and methods of fabrication of keypads.
Other objects will in part be obvious and will in part appear hereinafter.